Backlight assembly with optical film having positioning flange

ABSTRACT

A backlight assembly includes a frame, a light source, and at least one optical film. The light source is disposed on the frame. The optical film has at least one positioning flange. The positioning flange includes at least two contact edges configured to abut against at least one edge of the frame in at least two directions to hold the optical film in place relative to the frame.

This application claims the benefit of Taiwan application Serial No. 093105611, filed Mar. 3, 2004, the subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a backlight assembly, and more particularly to a backlight assembly whose optical films are held in the frame while the positioning flanges of the optical films are configured to abut against the edges of the frame in a number of directions.

2. Description of the Related Art

Featured by the advantages of having a light weight slim appearance, low power consumption and low radiation, the liquid crystal display (LCD) has gained a rapid advance in manufacturing technology and has been widely applied in electronic devices such as the personal digital assistant (PDA), notebook, digital still camera, digital video recorder, mobile phone, computer monitor and TV screen. Further, due to the long-term R&D investment and the adoption of large-scale manufacturing facilities, the quality of LCD device continues to improve while the price continues to decline. Consequently, the application of LCD is growing wider and wider. Since the display panel of an LCD is not self-luminous, a backlight assembly is required to provide necessary light for the display panel.

Referring to FIG. 1A, a diagram of a conventional backlight assembly is shown. In FIG. 1A, a backlight assembly 10 includes a frame 11, a light guide plate 12 and one or more optical films 13, wherein the bottom surface of the optical film 13 can be adhered to the top surface of the light guide plate 12 by means of adhesive tape (not shown in FIG. 1A). One lateral side of the optical film 13 has flanges 13 a and 13 b; wherein the flanges 13 a and 13 b respectively have openings 13 c and 13 d for respective bolts 15 a and 15 b to pass through. The optical film 13 is fixed to the frame 11 by inserting the bolts 15 a and 15 b through the openings 13 c and 13 d and screwing the bolts 15 a and 15 b into respective screw holes (not shown in FIG. 1A) in the frame 11.

Referring to FIG. 1B, another diagram of a conventional backlight assembly is shown. In FIG. 1B, a backlight assembly 20 includes a frame 21, a light guide plate (not shown in FIG. 1B) and one or more optical films 23, wherein the light guide plate 22 and the optical film 23 are both fixed within. The frame 21 has hooks 21 a and 21 b. One lateral side of the optical film 23 has flanges 23 a and 23 b, while the other lateral side of the optical film 23 has flanges 23 e and 23 f, wherein the flanges 23 a and 23 b. The flanges 23 a and 23 b have openings 23 c and 23 d for the respective bolts 25 a and 25 b to pass through. The flanges 23 e and 23 f respectively have openings 23 g and 23 h. The flanges 23 e and 23 f are fastened to the frame 21 by seating the openings 23 g and 23 h wherein the openings 23 g and 23 h can be hooked to the hooks around the respective hooks 21 a and 21 b. When the bolts 25 a and 25 b, inserted through the respective openings 23 c and 23 d, are screwed in respective screw holes in the frame 21 (not shown in FIG. 1B) and the openings 23 g and 23 h are hooked to the hooks 21 a and 21 b, the optical film 23 will be fixed to the frame 11.

It can be seen from the above disclosure that the conventional optical film is fixed to the frame by means of securing parts such as adhesive tape, bolts or hooks. Consequently, the additional securing parts increase the production cost, and are time-consuming to fasten. Moreover, since the conventional method according to FIG. 1A cannot fix the whole optical film precisely, the optical film is easily wrinkled, leading to a significant deterioration of luminance quality. According to the conventional method, the openings for securing the screws around the hooks are formed by punching holes in an optical film. However, the scraps of optical film obtained from punching cannot be recycled, and it is wasteful to throw away those scraps of optical film. Another problem is that the more flanges that are used the more likely light leakage will occur. Although the flanges 23 e and 23 f can be covered by shielding tape to reduce light leakage, additional tape costs are incurred. Furthermore, it is very difficult to separate the optical film from the light guide plate, because the optical film is tightly adhered to the light guide plate by adhesive tape.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a backlight assembly, which fixes an optical film in at least two directions by using a number of contact edges of each of the positioning flanges of the optical film to abut against at least one edge of the frame in at least two of directions. The invention not only improves the reliability of fixing the optical film but also avoids serious light leakage caused if too many flanges are used. Besides, no additional securing parts such as bolts or hooks are needed in the invention, so the expenditures for parts can be reduced. Moreover, no opening is required to be formed in the optical film, so material waste also can be reduced.

To satisfy this object of the invention, a backlight assembly including a frame, a light source, and at least one optical film is provided. The light source is disposed on the frame. The optical film has at least one positioning flange. The positioning flange includes at least two contact edges configured to abut against at least one frame side or member in at least two directions to hold the optical film in place relative to the frame.

According to another object of the invention, an optical film disposed on a frame is provided. The optical film includes a light incident surface and at least one positioning flange. The positioning flange includes at least two contact edges configured to abut against at least one frame side in at least two directions to hold the optical film in place relative to the frame.

Other objects, features, and advantages of the invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram of a conventional backlight assembly;

FIG. 1B is another diagram of a conventional backlight assembly;

FIG. 2 is a exploded view of a backlight assembly according to the preferred embodiment of the invention;

FIG. 3 is a exploded view partially showing the optical film and frame in FIG. 2;

FIG. 4 is a perspective view of the optical film mounted to the frame in FIG. 3;

FIG. 5 is a plane view of an optical film with two round positioning flanges;

FIG. 6 is a plane view of an optical film with two oval positioning flanges; and

FIG. 7 is a plane view of an optical film with two pentagonal positioning flanges.

DETAILED DESCRIPTION OF THE INVENTION

Please refer to FIGS. 2˜4 at the same time. FIG. 2 is an exploded view of a backlight assembly according to the preferred embodiment of the invention; FIG. 3 is an exploded view partially showing the optical film and frame in FIG. 2; and FIG. 4 is a perspective view of the optical film mounted to the frame in FIG. 3. In FIG. 2, a backlight assembly 30 includes a frame 31, a light guide plate 32, a light-shielding layer 34, and at least one optical film. An optical film 33 is exemplified in the disclosure of the invention. The frame 31 at least includes frame sides 31 a, 31 b and 31 c, wherein the frame side 31 a connects the two frame sides 31 b and 31 c. The frame has a rectangular accommodating area for receiving the optical film. The accommodating area is bounded by side borders defined by the inner edges of the frame sides such as sides 31 a, 31 b and 31 c, which intersect at four corners. The light source disposed on the frame 31 of the backlight assembly 30 is located under a surface of the light guide plate 32 or located at a side of the light guide plate 32.

The optical film 33 includes a light incident surface 33 a and at least one positioning flange, wherein the positioning flange is disposed on the peripheral of the light incident surface 33 a. Each of the positioning flanges has at least one contact edge for abutting against at least one side of the frame 31 in different directions such as two perpendicular directions. In practical application, the shape of the positioning flange is polygonal. In this embodiment of the invention, the rectangular positioning flanges 33 e and 33 f are exemplified for illustrating the optical film 33 mounted to the frame 31. Moreover, the shape of the optical film 33 approximates a rectangle or a polygon in practical applications, and is exemplified by the rectangular optical film 33 in the present preferred embodiment. Additionally, the positioning flanges 33 e and 33 f are disposed at two consecutive (adjacent) corners of the optical film 33. If the light incident surface 33 a is regarded as the main body of the optical film 33, the contact edges 40 a and 40 b of the positioning flange 33 e form a shoulder of the optical film 33, and the contact edges 41 a and 41 b of the positioning flange 33 f form the other shoulder of the optical film 33.

Please refer to FIG. 3 and FIG. 4. The contact edges 40 a and 40 b of the positioning flange 33 e abut against the respective sides 31 b and 31 a of the frame 31 in two perpendicular directions, while the positioning flange 33 e is inserted into a positioning recess 31 j of the frame side or frame member 31 b. Similarly, the contact edges 41 a and 41 b of the positioning flange 33 f (FIG. 2) abut against the respective frame sides 31 c and 31 a in a number of directions, while the positioning flange 33 f is inserted into a positioning recess 31 k in the frame side 31 c. As can be seen in FIG. 3 at 31 j, the recesses project outwardly of the adjacent borders of both sides 31 a and 31 b bounding the accommodating area of the frame (the inner edges of the frame sides). Accordingly, the optical film 33 is fixed to the frame 31 in at least two directions, the x-direction and the y-direction for instance. Besides, the light-shielding layer 34, as shown in FIG. 2, is used for covering the positioning flanges 33 e and 33 f of the optical film 33 to prevent light leakage from occurring.

However, anyone who is skilled in the art will realize that the technique of the invention is not limited thereto. For example, the light-shielding layer 34 can be replaced by light-shielding adhesive tape or a light-shielding rib to cover the positioning flanges 33 e and 33 f of the optical film 33. Also, the positioning flange of the optical film can be round, oval, pentagonal, or in another shape. In FIG. 5, an optical film 50 has two round positioning flanges 51 a and 51 b, wherein the contact edge 52 a of the positioning flange 51 a abuts against at least one corresponding frame side in a number of directions and the contact edge 52 b of the positioning flange 51 b abuts against at least one corresponding frame side in a number of directions. In FIG. 6, an optical film 60 has two oval positioning flanges 61 a and 61 b, wherein the contact edge 62 a of the positioning flange 61 a abuts against at least one corresponding frame side in a number of directions and the contact edge 62 b of the positioning flange 61 b abuts against at least one corresponding frame side in a number of directions. In FIG. 7, an optical film 70 has two pentagonal positioning flanges 71 a and 71 b, wherein the contact edge 72 a of the positioning flange 71 a abuts against at least one corresponding frame side in several directions and the contact edge 72 b of the positioning flange 71 b abuts against at least one corresponding frame side in several directions.

Although two positioning flanges of the optical film are exemplified in the preferred embodiment of the invention, the object of fixing the optical film to the frame can be achieved by using only one positioning flange, as long as the contact edges of the positioning flange disposed at the optical film abut against the frame side in a number of directions. Besides, if a couple of optical films have to be fixed to the frame, only the optical film placed on the top needs to have one or more positioning flanges for abutting against the frame side; in other words, there is no need for each optical film to have positioning flanges.

According to the aforementioned description, the backlight assembly disclosed in the preferred embodiment, which uses a number of contact edges of one or more positioning flanges of at least one optical film to abut against at least one frame side in a number of directions to hold the optical film in place relative to the frame, not only improves the reliability of fixing the optical film to the frame but also avoids serious light leakage if too many flanges are disposed on the optical film. Besides, no additional securing parts such as bolts or hooks for the fixation of the optical film are needed in the invention, so the expenditures for securing parts can be reduced. Moreover, no opening is required to form in the optical film, and material waste can be further reduced.

While the invention has been described by way of examples and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures. 

1. A backlight assembly, comprising: a frame; a light source disposed on the frame; at least one optical film having a shape that approximates a rectangle, and having two positioning flanges located at two adjacent corners, and at a same side of the optical film, wherein each positioning flange includes at least two contact edges configured to abut against at least one edge of the frame in at least two directions to hold the optical film in place relative to the frame; and a light-shielding layer for covering the positioning flanges of the optical film.
 2. The backlight assembly according to claim 1, wherein the optical film and the positioning flanges are formed in a single body.
 3. The backlight assembly according to claim 1, wherein each positioning flange located at one corner of the optical film forms a shoulder profile.
 4. The backlight assembly according to claim 1, wherein the shape of each positioning flange is a polygon.
 5. The backlight assembly according to claim 1, wherein the contact edges of each positioning flange are oriented to oppositely abut corresponding edges of the frame in two perpendicular directions to hold the optical film in place relative to the frame.
 6. The backlight assembly according to claim 5, wherein the frame has a rectangular accommodating area, having four side borders and corners at intersections of said side borders, configured to receive the optical film, the frame having a recess projecting outwardly of the side borders into sides of the frame in perpendicular directions from at least one of the corners, each positioning flange being received in the one of the corners so that the contact edges of the positioning flange are oriented to abut respective edges of the frame in the recess in two perpendicular directions to hold the optical film in place relative to the frame.
 7. A backlight frame structure comprising: a polygonal accommodating area, bounded by at least four side borders including first, second and third side borders, configured to receive at least one optical film of corresponding shape, wherein the first side border has a first end and a second end and the second and third side borders intersect the first border respectively at the first end and the second end; first, second and third frame members formed along the first, second and third side borders, respectively; a first recess at the intersection of first and second side borders projecting into the first and second frame members, outwardly of both said first side border and said second side border; and a second recess at the intersection of first and third side borders projecting into the first and third frame members, outwardly of both said first side border and said third side border, wherein said first recess and said second recess are shaped to receive a correspondingly shaped flange of the optical film, edges of the frame members bounding the first and second recesses, oriented to oppositely abut against contact edges of the flange of the optical film in at least two directions to hold the optical film in place relative to the frame.
 8. The backlight frame structure according to claim 7, wherein the contact edges of the frame members bounding the first and second recesses are oriented to abut against the contact edges of the flange in two perpendicular directions to hold the optical film in place relative to the frame.
 9. The backlight frame structure according to claim 7, wherein the correspondingly shaped flange of the optical film is located at a corner of the optical film and forms a shoulder profile.
 10. The backlight frame structure according to claim 7, wherein the shape of the correspondingly shaped flange is a polygon.
 11. The backlight frame structure according to claim 7, wherein the shapes of the accommodating area and the optical film approximate a rectangle.
 12. The backlight frame structure according to claim 7, wherein the optical film and the flange are formed in a single body.
 13. The backlight frame structure according to claim 7, wherein the optical film comprises two flanges located at two adjacent corners of the optical film.
 14. The backlight frame structure according to claim 13, wherein the flanges are located at the same side of the optical film. 